DescriptionThis species can reach a size of about 3 mm. The shape of the body is characteristic. The head is thin on the front, foot edges clearly protruding at its sides. Behind the head, the body maintains the same width until the end of the notum, where it expands appreciably sideways, ending in a short, wide tail. The body is coloured beige and could have some greenish tones. The body is covered with white scores but for two areas on the sides of the head, where the eyes are located, the margins of the body and where the pattern of white scores forms a sort of ridges or undulations. In the dorsum there are two areas of higher white spot concentration, one in the head region from the front end to the first third of the length of the animal, and the other, narrower, at the end of the notum. Foot white scores are much less abundant than in the notum. Tail white spot density is also less than on the notum, but much greater than on the foot. On a light background and by body translucency, there is a series of dark scores on the margins of the notum. The foot protrudes behind the notum as a short and rounded tail, semitransparent and with white scores. Below the right rear part of the notum, between it and the foot, there are 4 small gill leaves.

BiologyFrom this species it is only known that lives among algae and in Posidonia oceanica rhizomes.

Etymology

Runcina. From Latin “runcina”, carpenter’s plane, a tool used to smooth the wood’s surface.

Bahiensis, from “the bay”, meaning the Algeciras bay (Spain), where the two type specimens used to describe the species were found.

DistributionRuncina bahiensis is a very rare species which, so far, only two specimens have been collected in the Strait of Gibraltar (Cervera et al., 1991) that were used to describe the species, two other specimens in the Catalan Costa Brava, which are the second worldwide cite for the species (Correa, 2014) and a few more specimens (attached pictures) found by Enric Madrenas (2014, pers. comm) also in the Costa Brava.